New Perspectives on Foot Segment Forces and Joint Kinetics-Integrating Plantar Shear Stresses and Pressures with Multi-segment Foot Modeling

The role of the many small foot articulations and plantar tissues in gait is not well understood. While kinematic multi-segment foot models have increased our knowledge of foot segmental motions, the integration of kinetics with these models could further advance our understanding of foot mechanics and energetics. However, capturing and effectively utilizing segmental ground reaction forces remains challenging. The purposes of this study were to (1) develop methodology to integrate plantar pressures and shear stresses with a multi-segment foot model, and (2) generate and concisely display key normative data from this combined system. Twenty-six young healthy adults walked barefoot (1.3 m/s) across a pressure/shear sensor with markers matching a published 4-segment foot model. A novel anatomical/geometric template-based masking method was developed that successfully separated regions aligned with model segmentation. Directional shear force plots were created to summarize complex plantar shear distributions, showing opposing shear forces both between and within segments. Segment centers of pressure (CoPs) were shown to be primarily stationary within each segment, suggesting that forward progression in healthy gait arises primarily from redistributing weight across relatively fixed contact points as opposed to CoP movement within a segment. Inverse dynamics-based normative foot joint moments and power were presented in the context of these CoPs to aid in interpretation of tissue stresses. Overall, this work represents a successful integration of motion capture with direct plantar pressure and shear measurements for multi-segment foot kinetics. The presented tools are versatile enough to be used with other models and contexts, while the presented normative database may be useful as a baseline comparison for clinical work in gait energetics and efficiency, balance, and motor control. We hope that this work will aid in the advancement and availability of kinetic MSF modeling, increase our knowledge of foot mechanics, and eventually lead to improved clinical diagnosis, rehabilitation, and treatment.

Closing the Wearable Gap-Part II: Sensor Orientation and Placement for Foot and Ankle Joint Kinematic Measurements

The linearity of soft robotic sensors (SRS) was recently validated for movement angle assessment using a rigid body structure that accurately depicted critical movements of the foot–ankle complex. The purpose of this study was to continue the validation of SRS for joint angle movement capture on 10 participants (five male and five female) performing ankle movements in a non-weight bearing, high-seated, sitting position. The four basic ankle movements—plantar flexion (PF), dorsiflexion (DF), inversion (INV), and eversion (EVR)—were assessed individually in order to select good placement and orientation configurations (POCs) for four SRS positioned to capture each movement type. PF, INV, and EVR each had three POCs identified based on bony landmarks of the foot and ankle while the DF location was only tested for one POC. Each participant wore a specialized compression sock where the SRS could be consistently tested from all POCs for each participant. The movement data collected from each sensor was then compared against 3D motion capture data. R-squared and root-mean-squared error averages were used to assess relative and absolute measures of fit to motion capture output. Participant robustness, opposing movements, and gender were also used to identify good SRS POC placement for foot–ankle movement capture.

Biomechanical Considerations in Foot and Ankle Circular External Fixation: Maintenance of Wire Tension

Initial tensioning of the forefoot wires to 130 kg followed by simultaneous tensioning of the calcaneal wires to 90 kg and using the rigid double-row foot plate closed anteriorly via threaded rods produce maximum preservation of the initial wire tension during foot circular external fixation.

Midtarsal locking, the windlass mechanism, and running strike pattern: A kinematic and kinetic assessment

Changes in running strike pattern affect ankle and knee mechanics, but little is known about the influence of strike pattern on the joints distal to the ankle. The purpose of this study was to explore the effects of forefoot strike (FFS) and rearfoot strike (RFS) running patterns on foot kinematics and kinetics, from the perspectives of the midtarsal locking theory and the windlass mechanism. Per the midtarsal locking theory, we hypothesized that the ankle would be more inverted in early stance when using a FFS, resulting in decreased midtarsal joint excursions and increased dynamic stiffness. Associated with a more engaged windlass mechanism, we hypothesized that a FFS would elicit increased metatarsophalangeal joint excursions and negative work in late stance. Eighteen healthy female runners ran overground with both FFS and RFS patterns. Instrumented motion capture and a validated multi-segment foot model were used to analyze midtarsal and metatarsophalangeal joint kinematics and kinetics. During early stance in FFS the ankle was more inverted, with concurrently decreased midtarsal eversion (p < 0.001) and abduction excursions (p = 0.003) but increased dorsiflexion excursion (p = 0.005). Dynamic midtarsal stiffness did not differ (p = 0.761). During late stance in FFS, metatarsophalangeal extension was increased (p = 0.009), with concurrently increased negative work (p < 0.001). In addition, there was simultaneously increased midtarsal positive work (p < 0.001), suggesting enhanced power transfer in FFS. Clear evidence for the presence of midtarsal locking was not observed in either strike pattern during running. However, the windlass mechanism appeared to be engaged to a greater extent during FFS.

Human-like compliant locomotion: state of the art of robotic implementations

This review paper provides a synthetic yet critical overview of the key biomechanical principles of human bipedal walking and their current implementation in robotic platforms. We describe the functional role of human joints, addressing in particular the relevance of the compliant properties of the different degrees of freedom throughout the gait cycle. We focused on three basic functional units involved in locomotion, i.e. the ankle-foot complex, the knee, and the hip-pelvis complex, and their relevance to whole-body performance. We present an extensive review of the current implementations of these mechanisms into robotic platforms, discussing their potentialities and limitations from the functional and energetic perspectives. We specifically targeted humanoid robots, but also revised evidence from the field of lower-limb prosthetics, which presents innovative solutions still unexploited in the current humanoids. Finally, we identified the main critical aspects of the process of translating human principles into actual machines, providing a number of relevant challenges that should be addressed in future research.

Elastic energy within the human plantar aponeurosis contributes to arch shortening during the push-off phase of running

During locomotion, the lower limb tendons undergo stretch and recoil, functioning like springs that recycle energy with each step. Cadaveric testing has demonstrated that the arch of the foot operates in this capacity during simple loading, yet it remains unclear whether this function exists during locomotion. In this study, one of the arch׳s passive elastic tissues (the plantar aponeurosis; PA) was investigated to glean insights about it and the entire arch of the foot during running. Subject specific computer models of the foot were driven using the kinematics of eight subjects running at 3.1m/s using two initial contact patterns (rearfoot and non-rearfoot). These models were used to estimate PA strain, force, and elastic energy storage during the stance phase. To examine the release of stored energy, the foot joint moments, powers, and work created by the PA were computed. Mean elastic energy stored in the PA was 3.1±1.6J, which was comparable to in situ testing values. Changes to the initial contact pattern did not change elastic energy storage or late stance PA function, but did alter PA pre-tensioning and function during early stance. In both initial contact patterns conditions, the PA power was positive during late stance, which reveals that the release of the stored elastic energy assists with shortening of the arch during push-off. As the PA is just one of the arch׳s passive elastic tissues, the entire arch may store additional energy and impact the metabolic cost of running.

Multi-segment foot mobility in a hinged ankle-foot orthosis: the effect of rotation axis position

Hinged ankle-foot orthoses are prescribed routinely for the treatment of ankle joint deficits, despite the conflicting outcomes and the little evidence on their functional efficacy. In particular, the axis of rotation of the hinge is positioned disregarding the physiological position and orientation. A multi-segment model was utilized to assess in vivo the effect of different positions for this axis on the kinematics of foot joints. A special custom-made hinged orthosis was manufactured via standard procedures for a young healthy volunteer. Four locations for the mechanical axis were obtained by a number of holes where two nuts and bolts were inserted to form the hinge: a standard position well above the malleoli, at the level of the medial malleolus, at the level of the lateral malleolus, and the physiological between the two malleoli. The shank and foot were instrumented with 15 reflective markers according to a standard protocol, and level walking was collected barefoot and with the orthosis in the four mechanical conditions. The spatio-temporal parameters observed in the physiological axis condition were the closest to normal barefoot walking. As expected, ankle joint rotation was limited to the sagittal plane. When the physiological axis was in place, rotations of the ankle out-of-sagittal planes, and of all other foot joints in the three anatomical planes, were found to be those most similar to the natural barefoot condition. These preliminary measures of intersegmental kinematics in a foot within an ankle-foot orthosis showed that only a physiological location for the ankle mechanical hinge can result in natural motion at the remaining joints and planes.

Early heelstrike kinetics are indicative of slip potential during walking over a contaminated surface

OBJECTIVE

The objective of this study is to examine ground kinetics early in stance while walking on a contaminated surface and assess the potential of kinetics to quantify risk of slipping.

BACKGROUND

Prior studies of slipping have dismissed early ground kinetic data,and therefore no prior literature has been able to assess the viability of using these data to quantify slip potential.

METHOD

A total of 11 healthy male participants volunteered to walk over a force plate that was at random times contaminated with soap.Ground kinetics were measured by the force plate (2400 Hz), and heel displacement was quantified using high-speed video cameras (240 Hz) and retro-reflective markers.

RESULTS

The results indicated a significant reduction in shear force as early as 0.42 ms after heelstrike for contaminated trials, whereas for utilized coefficient of friction, a significant reduction was not seen until 11.34 ms. Heel displacements considered "safe" in the literature (< 30 mm) demonstrated proportionally different thresholds for shear force and utilized coefficient of friction.

CONCLUSION

The authors suggest that shear force in early stance shows more promise in quantifying slip potential as compared to utilized coefficient of friction given that (a) significant differences are seen earlier in shear than utilized coefficient of friction and (b) the threshold for utilized coefficient of friction, over which heel displacement stabilized to a"safe" value, exceeded values for utilized coefficient of friction that have been recommended as "safe".

APPLICATION

These results have wide implications for standards related to the design and testing of interventions to prevent injuries because of slipping.

Hydrodynamic pressure, carrying capacities, friction forces in biobearing gap

The present paper deals with the calculations of the pressure distributions, carrying capacities and friction forces derivations in a super- thin layer of biological synovial fluid inside the slide biobearing gap limited by a spherical, conical, cylindrical, parabolic, hyperbolic bone heads. There are also described unsteady and random flow conditions of the bio-bearing lubrication with the changes of the dynamic viscosity of the synovial fluid in the gap height in general.

Biomechanics of the foot in dance: a literature review

In any form of dance, great strain is placed on the lower extremity and the strong but sensitive foot. A large percentage of injuries to dancers involve the foot and ankle. Understanding the structure, biomechanics, and physics of the lower extremity helps to diagnose and evaluate the mechanics behind these injuries. The lower extremity function is complicated and needs to be studied carefully to understand its laws and principles. What often happens when injury occurs is that the dancer is not satisfying the natural requirements of movement through the joints. For example, her relevé is causing sickling and unstable foot positions because the forefoot is not strong enough and the leg external rotation and hip joint muscular support are not simultaneous with the heel raise. In the opposite direction, when the dancer is executing plié, the outcome of poor control of a weakened foot is strain on the passive supporting structures, such as the plantar ligaments, joint capsules, and plantar fascia. This leads to faulty bone alignment, increased bone load, and risk of overuse syndromes in various tissues.

Multisegmental foot modeling: a review

Over the past two decades, a number of multisegmental foot models have been developed in order to characterize foot kinematics. This paper reviews methods of multisegmental foot modeling, technical elements of the models, select clinical applications of the models, and future directions in this area of research. Technical areas discussed include angular derotation mechanisms and capture technology. Models discussed address two-, three-, four-, five-, and nine-segment approaches. Additional models which address foot segments using other definitions, are also discussed. Clinical applications of multisegmental foot models include pathologic gait characterization in rheumatoid arthritis, posterior tibial tendon dysfunction, and hallux rigidus. Areas of continued development, including soft tissue artifact and nomenclature, are also discussed.

Effect of toe and heel elevation on calculated tendon strains in the horse and the influence of the proximal interphalangeal joint

The sagittal alteration of hoof balance is a common intervention in horses, with corrective shoeing being one of the most frequently applied methods of managing tendonitis. However, the effect of toe or heel elevation on tendon strains is poorly understood. This study aimed to examine the effect of toe and heel wedges on the superficial digital flexor tendon, deep digital flexor tendon, and the third interosseous muscle or suspensory ligament strains using in vivo data and an accurate subject-specific model. Kinematic data were recorded using invasive markers at the walk and trot. Computerized tomography was then used to create a subject-specific model of an equine distal forelimb and strains were calculated for the superficial digital flexor tendon, the deep digital flexor tendon accessory ligament and the suspensory ligament for seven trials each of normal shoes, and toe and heel elevation. As the proximal interphalangeal joint is often ignored in strain calculations, its influence on the strain calculations was also tested. The deep ligament showed the same results for walk and trot with the heel wedge decreasing peak strain and the toe wedge increasing it. The opposite results were seen in the suspensory ligament and the superficial digital flexor tendon with the heel wedge increasing peak strain and the toe wedge decreasing it. The proximal interphalangeal joint was shown to be influential on the strains calculated with normal shoes and the calculated effect of the wedges. Our results imply that corrective shoeing appears to decrease strain in the tendon being targeted; the possibility of increases in strain in other structures should also be considered.

The influence of foot progression angle on the knee adduction moment during walking and stair climbing in pain free individuals with knee osteoarthritis

The external knee adduction moment during walking and stair climbing has a characteristic double hump pattern. The magnitude of the adduction moment is associated with the development and progression of medial compartment knee osteoarthritis (OA). There is an inverse relationship between the magnitude of the second peak adduction moment and foot progression angle (FPA). Increasing FPA beyond a self-selected degree of toe-out may further reduce the magnitude of this moment for persons with knee OA. In this study, subjects with medial compartment knee OA walked and climbed stairs using their natural (i.e. self-selected) and an increased FPA (i.e. self-selected+15 degrees of additional toe-out). Increasing FPA did not change the magnitude of the first peak adduction moment but it did significantly decrease the second peak during walking. The first peak moment during stair ascent was significantly greater for the increased FPA condition, and a significant reduction was noted for the second peak. No significant differences were noted during stair descent. These results suggest that walking with a toe-out strategy may benefit persons with early stages of medial knee OA.

The synovial joints of the human foot

The human foot is considered an organ with an assortment of tissues with different morphological characteristics and well defined limits, but effectively has a simple functionality when static that becomes extremely complex when in movement. Its complex structure, comprised of an elastic and resistant skin covering a bone framework, joints, muscles, tendons, veins and nerves, can be compared to an efficient mechanical assembly. After a long and extraordinary evolutive journey, the human foot has undergone numerous changes to perfect its function; it has lost most of its grabbing function whilst gaining new characteristics that have ultimately allowed the modern man to stand upright. The complex articular structure of the human foot consists of thirty four synovial joints, of which eighteen have curved surfaces and sixteen plane surfaces. Following the criteria set by the systematic, radiological and clinical anatomy, the Authors contribute further to the current knowledge on the ankle, tarsal (anatomic subtalar, transverse tarsal, cuneonavicular, intercuneiform and cuneocuboid), tarsometatarsal, intermetatarsal, metatarsophalangeal and interphalangeal joints and dorsal, plantar and interosseous ligaments of the human foot. The articular lines of the transverse tarsal (Chopart) and tarsometatarsal (Lisfranc) joints are particularly interesting and not only from a surgical point of view; through a straightforward identification of few reference points, it is possible to find the medial and lateral extremities of the Chopart's and Lisfranc's lines, the former pinpoints the boundary between the hindfoot and midfoot and the latter between the midfoot and forefoot.

In vivo talocrural and subtalar kinematics: a non-invasive 3D dynamic MRI study

BACKGROUND

To improve diagnostic accuracy, prevent injury, and reduce the effect of impairments on hindfoot function, an understanding of the combined in vivo kinematics of the talocrural and subtalar joints is critical. Therefore, the purpose of this study was to test the feasibility of quantifying talocrural and subtalar joint kinematics using fast-phase contrast (fast-PC) MRI, a noninvasive, in-vivo technique for the study of three-dimensional joint motion.

METHODS

Nine normal ankles and two ankles with a Stieda process were studied. Subjects were each placed supine in a 1.5 T MRI and asked to maintain a repeated dorsiflexion-plantarflexion movement while a full sagittal-oblique fast-PC dataset was acquired. The orientation and position of the calcaneus, talus, and tibia were individually quantified from these data.

RESULTS

The precision and accuracy of tracking calcaneal, talar, and tibial movement was excellent. The three-dimensional subtalar kinematics demonstrated that the talus and calcaneus do not move as a single unit. Most calcaneal-tibial supination occurred at the talocrural joint. The ankles with a Stieda process had markedly different kinematics from each other as well as from the normal group.

CONCLUSIONS

This study demonstrated that fast-PC MRI is a viable, precise, and accurate technique for studying hindfoot kinematics and is potentially a useful clinical diagnostic tool. The findings call into question the earlier anatomical studies on which much of clinical practice on the foot and ankle is based. Since a clear link was found between anatomical variation and altered rearfoot kinematics, future study is warranted.

Rear-foot, mid-foot and fore-foot motion during the stance phase of gait

This paper proposes a new protocol designed to track a large number of foot segments during the stance phase of gait with the smallest possible number of markers, with particular clinical focus on coronal plane alignment of the rear-foot, transverse and sagittal plane alignment of the metatarsal bones, and changes at the medial longitudinal arch. The shank, calcaneus, mid-foot and metatarsus were assumed to be 3D rigid bodies. The longitudinal axis of the first, second and fifth metatarsal bones and the proximal phalanx of the hallux were also tracked independently. Skin markers were mounted on bony prominences or joint lines, avoiding the course of main tendons. Trajectories of the 14 markers were collected by an eight-camera motion capture system at 100 Hz on a population of 10 young volunteers. Three-dimensional joint rotations and planar angles were calculated according to anatomically based reference frames. The marker set was well visible throughout the stance phase of gait, even in a camera configuration typical of gait analysis of the full body. The time-histories of the joint rotations and planar angles were well repeatable among subjects and consistent with clinical and biomechanical knowledge. Several dynamic measurements were originally taken, such as elevation/drop of the medial longitudinal arch and of three metatarsal bones, rear-foot to fore-foot rotation and transverse plane deformation of the metatarsus. The information obtained from this protocol, consistent with previous clinical knowledge, enhanced our understanding of the dynamics of the human foot during stance.

Intrinsic foot kinematics measured in vivo during the stance phase of slow running

An accurate kinematic description of the intrinsic articulations of the foot during running has not previously been presented, primarily due to methodological limitations. An invasive method based upon reflective marker arrays mounted on intracortical pins drilled into the bones was used in this study. Four male volunteers participated as subjects. Pins (1.6mm diameter) were inserted under local anaesthetic in the tibia, fibula, calcaneus, talus, navicular, cuboid, medial cuneiform and metatarsals I and V. A 10 camera motion analysis system was used for kinematic data capture and the ground reaction force was simultaneously measured. Segment motion relative to adjacent proximal segments was determined using helical axes projected into the coordinate system of the proximal segment. Coefficients of multiple correlation calculated to determine the strength of association between running style with and without the pins inserted indicated that the subjects had little restriction due to the inserted pins. Individual and mean results were presented for rotations defined in the planes of the proximal segment's coordinate system and showed frontal plane rotation of the talocrural joint (12.2+/-7.1 degrees ), which exceeded that of the subtalar joint (8.9+/-3.2 degrees ). Considerable mobility of the talonavicular joint was found (6.5+/-2.9 degrees , 13.5+/-4.1 degrees and 8.7+/-1.4 degrees in the sagittal, frontal and transverse planes, respectively). Furthermore, little, but non-negligible motion between the fibula and tibia was found (3.3+/-2.4 degrees in the sagittal plane). The presented data are of interest as input for future biomechanical modelling and clinical decision making in particular, concerning joint fusion.

The jargon of pedal movements

BACKGROUND

All areas of research have their own specialized terms. Typically jargon is used as a short cut among specialists to convey complex ideas with a few brief words or phrases. Several jargons traditionally have been used to describe movements of the foot and ankle. It has been long recognized that these terms have no uniform meanings, which leads to confusion when attempting to synthesize reports from different researchers. Although many researchers are aware of this problem, few seem to be aware of how pervasive it is within the published literature. This report focuses on the depth of variation in uses of the terms inversion and eversion and pronation and supination in describing foot motions.

METHODS

A survey was sent out via the Internet to three communities: biomechanists, clinical anatomists, and podiatrists. A similar survey was conducted of published articles that appeared during a 10-year period in 16 scientific journals. These surveys provide data on the use and interdependencies of how pronation and supination and inversion and eversion are defined.

RESULTS

There are at least 18 different working definitions of inversion and eversion and 20 working definitions of pronation and supination. Several of the definitions were shown to be mutually contradictory.

CONCLUSIONS

Specialists have failed to describe foot movements in a way that can be unambiguously interpreted. Mutual incomprehensibility of foot movements complicates the interpretive value of any report of foot movements. It is suggested that a new set of terms may help prevent this type of confusion in the future.

CLINICAL RELEVANCE

The lack of unambiguous descriptions in the research literature may mean that clinicians are not always applying treatment options in an appropriate manner. Greater clarity of meaning is required for both basic research and clinical applications.

Foot rotation—A potential target to modify the knee adduction moment

Isolating the particular joints/limb segments associated with knee adductor moment variability may provide clinically important data that could help to identify strategies to reduce medial tibiofemoral joint load. The aim of this study was to examine whether or not foot and thigh rotation during human locomotion are significant determinants of knee adductor moment variability. Three-dimensional gait analyses were performed on 32 healthy adult women (mean age 54+/-12 years, mean BMI 25+/-4 kg m(-2)) with radiologically normal knees. The relationships between foot rotation, thigh rotation and the external knee adduction moment were examined during early and late-stance phases of the gait cycle. The degree of foot rotation correlated significantly with the magnitude of the peak knee adduction moment during late stance (r=0.40, p=0.024). No significant associations were apparent between thigh rotation and the peak knee adduction moment. The association between foot rotation and the knee adduction moment in this study suggests that women who walk with external rotation at the foot reduce their knee adduction moment during late stance. This result implies that changes in foot kinematics can modify the medial tibiofemoral load during gait, which may be important in the prevention and management of knee osteoarthritis.

Factors associated with chronic plantar heel pain: a systematic review

Chronic plantar heel pain (CPHP) is one of the most common soft tissue disorders of the foot, yet its aetiology is poorly understood. The purpose of this systematic review was to examine the association between CPHP and the various aetiological factors reported in the literature. Seven electronic databases and the reference lists of key articles were searched in August 2005. The resulting list of articles was assessed by two independent reviewers according to pre-determined selection criteria and a final list of articles for review was created. The methodological quality of the included articles was assessed and the evidence presented in each of the articles was descriptively analysed. From the 16 included articles, body mass index in a non-athletic population and the presence of calcaneal spur were the two factors found to have an association with CPHP. Increased weight in a non athletic population, increased age, decreased ankle dorsiflexion, decreased first metatarsophalangeal joint extension and prolonged standing all demonstrated some evidence of an association with CPHP. Evidence for static foot posture and dynamic foot motion was inconclusive and height, weight and BMI in an athletic population were not associated with CPHP. The findings of this review should be used to guide the focus of prospective cohort studies, the results of which would ultimately provide a list of risk factors for CPHP. Such a list is essential in the development of new and improved preventative and treatment strategies for CPHP.

Stability of Lisfranc joints in ballet pointe position

BACKGROUND

Ballerinas develop stress fractures at the second metatarsal base associated with dancing en pointe. The purpose of this study was to evaluate the relative importance of the pointe shoe and the tarsometatarsal ligaments in Lisfranc joint stability en pointe.

METHODS

Eleven cadaver feet were dressed with pointe shoes, loaded in foot flat with ligaments intact, and loaded en pointe before and after sequential sectioning of the dorsal, interosseous, and plantar ligaments between the first and second metatarsals and cuneiforms. Relative motion between the first and second metatarsals and cuneiforms was determined radiographically.

RESULTS

No significant displacement of the Lisfranc joints occurred when the shod foot with intact ligaments was loaded in the foot flat or en pointe positions. Serial sectioning of the ligaments from dorsal to plantar in the shod foot en pointe demonstrated no change in alignment after the dorsal and interosseous ligaments were cut, but a significant change in alignment between the second metatarsal and second cuneiform was noted after the plantar ligament was cut (p < 0.0001). Removal of the pointe shoe after cutting the ligaments and applying a minimal (1 to 2 kg) load resulted in complete subluxation and diastasis through the first-second intermetatarsal and intercuneiform region. Replacing the shoe improved alignment en pointe with similar loading.

CONCLUSIONS

Both the pointe shoe and Lisfranc ligaments are important for Lisfranc region stability in feet en pointe. The plantar ligaments are major stabilizers of the Lisfranc region in the loaded, shod foot en pointe. Selection of a pointe shoe with adequate support may limit susceptibility to stress fracture of the second metatarsal base in ballerinas.

Hypermobility of the first tarsometatarsal joint

This article discusses hypermobility of the first tarsometatarsal joint.

Effects of the subtalar sling ankle taping technique on combined talocrural-subtalar joint motions

BACKGROUND

The findings of research on the effectiveness of ankle taping for protection against ligament injury have been inconsistent, and the topic remains controversial. The precise orientation of the force vectors created by tension within the various tape strip components of an ankle taping procedure may be a critical factor influencing the degree of motion restraint that is provided. We hypothesized that the addition of the subtalar sling component to the widely recognized standard (Gibney) ankle taping procedure would enhance restraint of ankle motion. This was a controlled laboratory study, with fully repeated measures (subjects served as their own controls).

METHODS

An ankle arthrometer was used to quantify anteroposterior (AP) translation and frontal plane inversion-eversion (I-E) tilt of the talocrural-subtalar joints under untaped and taped conditions in normal subjects. A 15-minute exercise session was conducted to loosen the tape before measurement of its effect on motion restraint.

RESULTS

The ankle taping procedure that incorporated the subtalar sling provided significantly greater restriction of postexercise AP translation (p < 0.001, eta(2) = 0.63) and postexercise I-E tilt (p < 0.001, eta(2) = 0.66).

CONCLUSIONS

The subtalar sling ankle taping procedure provides greater restriction of motions associated with ankle instability than the more widely used Gibney procedure.

Anatomy, biomechanics, and surgical approach to synovial folds within the joints of the foot

The presence of synovial folds in various joints of the foot has been previously documented. The function and clinical significance of these structures within the joint have not been established. Histologically they are considered anatomically different from a meniscus primarily owing to their makeup of loose connective tissue with nerve fibrils and several synovial cell layers. We hypothesize that the function of these folds is similar to that of the menisci: to increase joint congruity and stability. We further hypothesize that these folds will be present in joints of the foot that require greater stability. To demonstrate this, 41 fixated cadaveric feet were sectioned in the sagittal plane and the incidence and locations of the synovial folds were documented. Three fixated cadaveric feet were evaluated using a materials testing machine. The first metatarsophalangeal joint was incised, and the presence of the synovial fold was documented. The joint was then taken through its range of motion with and without the synovial fold while data on the force and displacement were collected. The steps were then repeated for the ankle joint. The results showed statistically stiffer ankle and first metatarsophalangeal joints with the synovial fold present, as determined by the stress-strain curve. On the basis of the presence and location of these synovial folds, we demonstrated arthroscopic surgical approaches to many of the documented joints that contain these folds. Because the folds contain synovial cells and vascular tissue, damage to them can result in considerable pain. In such cases, arthroscopic surgery would be of benefit. Further research may indicate whether they need to be salvaged during joint procedures to facilitate normal joint function or should be removed to reduce postoperative complications.

Clinical biomechanics of the peritalar joint

The peritalar joint includes the articulations between the talus and calcaneus and the talus and navicular. Motion between the talus and calcaneus is described most often as rotation about an axis that points medially, anteriorly, and superiorly. This motion is considered to be triplanar, with inversion, plantar flexion, and adduction occurring together, whereas eversion, dorsiflexion, and abduction are associated. Similar motions have been described between the talus and navicular. Foot deformity, such as a pes planus or a pes cavus foot type, and hindfoot or midfoot joint fusion can alter the biomechanics of the peritalar joint.

Multi-joint coordination in ballet dancers

In upright posture, we analyzed the multi-joint coordination during drawing ellipses with the foot in a horizontal plane in classical ballet dancers (Elite) and gymnasts who had no dance training (Novice). In both groups, the stability of the head and the trunk was similar. Furthermore, a comparatively simple synergy inter-relating the movements in the hip, knee and ankle joints, was revealed by the kinematic analysis. However, novices made larger errors in the eccentricity and orientation of ellipses than ballet dancers. Ankle angular excursions were smaller in novices than in dancers whereas hip angular excursions were larger. This study illustrates some rules underlying the ability of the nervous system to integrate multiple degrees of freedom of the body to master body balance while producing complex leg movement trajectories. This study offers a dynamical approach of the problem of redundancy.

Foot and Ankle Research Retreat: concensus statement

It is well recognized that the foot is a complex structure with 26 bones and over 30 articulations. Measuring its mechanics is a formidable task that is usually accomplished with a simplification of the system. The papers presented at this meeting provided some of the most current research in the area of multisegment foot modeling. The scientific discussions were rich as the small, intimate, and collegial environment encouraged an open flow of ideas. It was acknowledged that much work is still needed in the development of foot models to improve the measurement of foot mechanics. However, there was a strong sentiment among the participants to begin to apply these models to clinical problems. It was suggested that this be the focus of the next Foot and Ankle Research Retreat.

Peroneus brevis is a more effective evertor than peroneus longus

A primary function of the peroneus longus and peroneus brevis is to provide the eversion moment necessary to balance the opposing inversion moments. Surgeons often deal with the loss of or need to sacrifice one of these tendons. This study compares the evertor mechanisms of the peroneus brevis and peroneus longus muscle. This is accomplished in a cadaver model in which the performance of each of the muscle tendons during early heel rise of gait is assessed utilizing the same tendon loads in each so that force is not a variable. Six fresh-frozen cadaver foot-ankle specimens were studied during a simulated early heel rise phase of the gait cycle. The study compared the effect of the peroneus brevis and peroneus longus by separately applying the same load to the each of the tendons. At the talonavicular joint, the peroneus brevis loaded condition externally rotated the navicular 2.1 degrees more than when the peroneus longus was loaded. At the subtalar joint, the peroneus brevis loaded condition resulted in 0.9 degrees more calcaneus valgus relative to the talus than was present during the peroneus longus loaded condition. The experimental data support the hypothesis that the peroneus brevis tendon mechanism is more effective than is the peroneus longus mechanism in rotating the navicular externally and the calcaneus into valgus. This has clinical implications for assisting surgeons in trying to preserve evertor function.

Land mine injury: functional testing outcome

We present a case of a war patient treated with external fixation for a complex land mine injury involving the fracture of the tibial and fibular bones, which occurred at the front line during the war in Croatia and Bosnia and Herzegovina. Excessive destruction and foreign body penetration into the distal two-thirds of the right leg and foot endangered not only the patient's lower extremity but his life as well. Nevertheless, the patient's life, as well as extremity, was saved due to an intensive treatment. A 100-month follow-up showed a bridge callus between the tibia and fibula, tibial bone defects, tibial anterior angulation of 5 degrees, and arthrosis of the right upper ankle joint. Despite a relatively unsatisfactory X-ray finding, the functional testing on the dynamometry system Cybex 300 showed surprisingly good results. There was a satisfactory functional recovery of the treated extremity: the patient could walk without any help even on rocky grounds and was actively involved in his sheep farm duties.

Hypermobility of the first ray: a critical review of the literature

The authors provide a detailed review of the available literature regarding first ray sagittal plane direction and range of motion with special emphasis on whether or not hypermobility of the first ray can truly be supported as a definable clinical entity. They also describe a novel clinical test for assessing sagittal plane instability of the first ray. The authors believe that this test, when combined with previously defined clinical tests, helps to identify those few patients that would benefit from an arthrodesis procedure of the medial pillar of the foot for the treatment of the hallux valgus deformity.

Biomechanics of the first ray. Part IV: the effect of selected medial column arthrodeses. A three-dimensional kinematic analysis in a cadaver model

This study is the fourth in a series of investigations on the biomechanics of the first ray, this part focusing on open kinetic chain range of motion simulating the clinical examination. Segmental sagittal range of motion of the medial column was measured on intact cadaver specimens and compared to various simulated medial column arthrodesis patterns. These arthrodeses included the first metatarsocuneiform, first metatarsocuneiform-intercuneiform, naviculocuneiform, and talonavicular joints. The specimens were mounted to a test apparatus that was comprised of a modified ankle-foot orthosis which held the ankle and rearfoot in fixed neutral position. Additionally, the lesser metatarsus was affixed to the test apparatus while the first ray was left free to be manipulated via a carbon fiber rod attached to a pneumatic actuator. A 24.5-N (5.5-lb) sagittal plane load was applied to the first ray while the specimen was held rigidly in the apparatus. The first ray was manipulated using a repeated measures design. Data were collected for each osseous segment of the medial column using a radiowave tracking system. Kinematic data were collected and statistically analyzed. Results demonstrated in intact specimens that the naviculocuneiform, first metatarsocuneiform, and talonavicular joints contributed an average of 50%, 41%, and 9% of total first ray sagittal plane range of motion, respectively. Furthermore, first ray range of motion was significantly reduced with all of the simulated arthrodeses of the medial column (p < .05). These findings suggest that first ray range of motion when evaluated clinically is a blend of motions of joints comprising the medial column.

A biomechanical model of the foot: the role of muscles, tendons, and ligaments

A biomechanical model of the foot is developed and analyzed to determine the distribution of support under the metatarsal heads, the tension in the plantar aponeurosis, and the bending moment at each of the joints of the foot. This model is an extension of our earlier work to include the role of muscles, tendons, and ligaments. Two cases are presented: in the first the center of gravity of the body is over the mid foot, and in the second, the center of gravity is anterior, over the metatarsals, and no support is provided by the heel. The model shows the extent to which the muscles reduce the force in the supporting ligaments at each of the joints and decrease the tension in the plantar aponeurosis, and that this effect is more pronounced when the center of gravity of the body is moved forward.